When determining a balancing solution for a rotor, vibration magnitude and phase data are typically required. In most two-spool gas turbine engines, the phase data of the high-pressure spool is not available during normal operation. Accordingly, the acquisition of vibration and phase data for the balancing of the high-pressure spool is typically conducted while the high-pressure spool is rotated at sub-idle speeds and also while the engine is partially disassembled in order to visually expose a portion of the high-pressure spool during balancing. Since the dynamic characteristics of the high-pressure spool can be quite different at normal operating speeds than they are at reduced, sub-idle speeds, the balancing solution acquired under such reduced speed conditions may not necessarily be ideal for typical operating conditions of such gas turbine engines.
Improvement is therefore desirable.